12.4.3 Setting guidelinesThe parameters for the local acceleration logic functions are set via the local HMI orPCM600.GlobalBaseSel: Selects the global base value group used by the function to define (IBase),(VBase) and (SBase).Set ZoneExtension to Enabled when the first trip from selected overreaching zone shall beinstantaneous and the definitive trip after autoreclosure a normal time-delayed trip.Set LossOfLoad to Enabled when the acceleration shall be controlled by loss-of-load inhealthy phase(s).LoadCurr must be set below the current that will flow on the healthy phase when one ortwo of the other phases are faulty and the breaker has opened at remote end (three-phase).Calculate the setting according to equation 176.min0.5 LoadBaseILoadCurr I×=EQUATION1320 V1 EN (Equation 176)where:ILoadmin is the minimum load current on the line during normal operation conditions.The timer tLoadOn is used to increase the security of the loss-of-load function for exampleto avoid unwanted release due to transient inrush current when energizing the line powertransformer. The loss-of-load function will be released after the timer tLoadOn haselapsed at the same time as the load current in all three phases are above the settingLoadCurr. In normal acceleration applications there is no need for delaying the release, soset the tLoadOn to zero.The drop-out timer tLoadOff is used to determine the window for the current releaseconditions for Loss-of-load. The timer is by default set to 300ms, which is judged to beenough to secure the current release.The setting of the minimum current detector, MinCurr, should be set higher than theunsymmetrical current that might flow on the non faulty line, when the breaker at remoteend has opened (three-phase). At the same time it should be set below the minimum loadcurrent transfer during normal operations that the line can be subjected to. By default,MinCurr is set to 5% of IBase.Section 12 1MRK 506 334-UUS AScheme communication406Application manual
